The mosaic phase of the Pb/Si(111) system, consisting of 1/6ML Pb and 1/6ML Si atoms, was studied with both experimental (STM, STS, SRPES) and theoretical DFT calculations. The aim of the present work is to analyze the relation between a local atomic arrangement and character of the electronic structure. The combination of the applied experimental and theoretical methods provides complex and detailed picture of the local character of the mosaic phase.
In particular, we have identified thirteen characteristic structural motives of the nearest neighbour atoms from the experimental STM images. Detailed analysis using STS spectra and lock-in LDOS maps of the selected motives have shown strong correlation between the local atomic arrangement and the character of electronic structure showing the variation between metallic and semiconducting character of the surface layer.
In second step, we have performed DFT calculations using fast local orbital code FIREBALL of selected mosaic patterns, having 6x6 periodicity, derived from experimental images. Those calculations provide direct insight into the atomic rearrangement and the comparison of energetic stability among the different mosaic patterns. Surprisingly, we have found the most stable structure formed by alternating ideal infinite lines of Pb and Si atoms respectively. In addition, we compared both experimental and theoretical STM images. Brief discussion of the influence of Schottky barrier on experimental STM measurements will be provided.
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